ACTG efficacy studies have thus far required long periods of clinical follow up, and/or development of endpoint events, before indications of therapeutic efficacy could be obtained. The objective of the current proposal is to identify valid measurements of immune response that could serve as markers (a) for effective immunological staging for entry into treatment protocols, (b) and/or as indicators of near-term and/or long-term prognosis, (c) and/or as indicators of efficacy or lack of efficacy of treatment regimens for individuals with HIV infection. Such measurements would in addition have to be feasible components of multi-site clinical protocols. The specific aims of this proposal are: (1) To evaluate circulating cytokine levels and in vitro production of cytokines as surrogate markers for both general and HIV-specific immune status, and/or as markers for prognosis or response to therapy, using methods that could be applied widely in the ACTG program; (2) Specifically, to measure circulating levels and in vitro unstimulated and mitogen-, alternate antigen (influenza virus)-, or HIV-specific antigen-stimulated production of tumor necrosis factor-alpha), interleukin-6 (IL-6), and interferon-gamma (IFN-gamma) as such markers; (3) In addition, to determine whether in vitro unstimulated or stimulated production of the cytokines also results in activation and/or proliferation detectable by flow cytometric methods (marker expression analysis) or cell cycle analysis; (4) Initially t measure the cytokine responses of a cross-section of individuals who are normal seronegatives, recipients of an HIV vaccine preparation, or seropositive and at various stages of HIV infection, with concurrent and subsequent analysis of individuals who are entered into specific therapeutic protocols (e.g., ACTG #117 and #175) and followed longitudinally. The most appropriate of different methods to conduct the assays will be determined, with attention to ease and validity for eventual adoption by the many ACTG units. It is anticipated that the HIV-specific production of IFN-gamma will be an important and predictive marker on its own or in combination with CD4+ lymphocyte counts or analyses of monokine production (TNF-alpha and/or IL-6) or analyses of cellular expression of activation/proliferation markers.